Internal resistance fluid pressure clutch or brake



Oct. 1, 1957 w. G. MERRITT 2,808,130

INTERNAL RESISTANCE FLUID PRESSURE CLUTCH OR BRAKE Filed Aug. 9. 1954 4 as f {y 1 /6 l l 8 /7 7 INVENTOR WILLIAM G. MERRITT BY w ATTORNEY United States Patent Q P INTERNAL RESISTANCE FLUID PRESSURE CLUTCH OR BRAKE William G. Merritt, Ephrata, Wash., assignor of forty percent to Frank Therriault and Selma Therriault, Ephrata, Wash.

Application August 9, 1954, Serial No. 448,699

4 Claims. (Cl. 188-90) This invention relates to fluid pressure operated devices such as clutches and brakes. More particularly, this invention is concerned with a control system for varying the fluid pressure loading on one or more reversible positive displacement pumps used as a fluid pressure clutch or brake.

The basis of the present invention derives from the known fact that if the high pressure outlet of a positive displacement pump is closed, and the low pressure inlet side of the pump is connected to a fluid reservoir, the pump rotor will be positively locked against rotation. By varying the degree of restriction of the outlet of the pump commensurately with the extent of opening of the pump inlet, various degrees of resistance to rotation of the pump rotor may be achieved. There has been a considerable development of devices of this broad general type for use as brakes and clutches, but none to date have enjoyed substantial commercial success for a number of reasons.

Accordingly, it is the principal object of the present invention to provide a control system for varying the fluid pressure load on the rotors of positive displacement pumps used as clutches or brakes, which will overcome previous deficiencies in apparatus of this type.

It is a further object of this invention to provide a control system for devices of this type in which a remote master control valve may be used to control the loading on one or a plurality of positive displacement pump rotors which will be effective irrespective of the direction of rotation of the rotor.

A further object is to provide an adjustable relief valve in the system so connected as to by-pass the control valve on the high pressure side of the system, in the event that fluid pressure loading rises above a predetermined maximum.

A still further object of this invention is to provide in a system of this kind a heat exchange coil through which fluid circulating from the high pressure side of the pumps must pass before returning to the reservoir.

Other objects will be apparent from the following description read in conjunction with the attached sheet of drawing in which the single figure shows in diagrammatic form a preferred embodiment of the invention.

Referring now to the attached drawing, there are shown a plurality of positive displacement pumps 10, 11 and 12. The pump 11 is shown in section in order to illus-' trate the working parts thereof. The latter include a rotor 13, which is mounted eccentrically with respect to the outer casing 14. A single vane 15 is spring pressed as at 16 into engagement with the outer periphery of the rotor and further serves to divide the pump housing into two sides 17 and 18. For clockwise rotation of the rotor, 18 will be the high pressure side, and conversely, for counterclockwise rotation, 17 will be the high pressure side. It will of course be understood that three pumps are shown in the drawing merely for illustrative purposes. The actual number used is not critical.

:The fluid supplyfor the entire control system is in- 2,808,130 Patented Oct. 1, 1957 dicated by the reservoir 19. The master control valve shown at 20, an automatic reversing valve shown at 21, and the pressure relief valve shown at 22, constitute together with the reservoir and the pump, the basic components of the system.

Corresponding sides of the pumps are connected by a pair of manifolds 23 and 24, and therefore one of these manifolds will be under high pressure and the other under low pressure, depending upon the direction of rotation of the pumps. The function of the automatic reversing valve 21 is to insure that regardless of the direction of rotation of the pumps, of the two lines which ultimately carry the working fluid from the pumps to the master control valve, one will always be the high pressure line and the other will always be the low pressure line. The advantages of such an arrangement are that the remote control valve can be greatly simplified. Line 25, therefore, will always be the high pressure line while 26 will always be the low pressure line.

The automatic reversing valve 21 includes three interconnected slidably mounted pistons 27, 28 and 29. Pilot lines 30 and 31 supply fluid pressure to the pistons 27 and 29 to shift the valve 21 to one or the other of its ends of travel depending on the direction of rotation of the pumps. If we assume, therefore, that the direction of rotation of the pumps is clockwise as indicated on the drawing, then manifold 23 will be the high pressure manifold and this pressure transmitted through the pilot line 31 will serve to maintain the valve 21 in the position shown, thus affording free communication between the high pressure manifold and the high pressure line 25. If, on the other hand, the direction of rotation of the pumps is reversed, manifold 24 becomes the high pressure line and fluid pressure transmitted through pilot line 30 will act on the piston 27 to move the entire valve assembly to the opposite end of its path of travel. When in this position, the piston 28 will occupy a position to the left of the high pressure line 25 and, therefore, there will be free communication between the manifold 24 and the high pressure line 25. The piston 29 will be positioned to uncover the lower end of low pressure line 26 which will then have free communication with manifold 23. At the same time, the piston 27 will be positioned to close the lower end of line 32 so that high pressure fluid cannot gain access to the low pressure line 26. I

The master control valve 20 includes a pair of interconnected pistons 33 and 34, constituting valve members slidably mountedrin a housing. In the position shown, piston 33 is positioned to block the high pressure outlet of line or passageway 25, and the piston 34 is positioned to allow free communication betweeen the reservoir 19 and the low pressure or inlet lineor passageway 26." With the valve 29 in this position, the rotors of all three pumps, will be positively locked against rotation.

In some applications, conditions could obviously occur giving rise to fluid pressures above and beyond safe working pressures of the control system. To provide for Under these "conditions, there will be a considerable amount of heat generated in the working fluid and; therefore, a heat exchange coil 38 may be connected bejtween the reservoir and the high pressure pump outlet."

. 3 V The valve 22 discharges high pressure fluid through this heat exchange coil in order that it may be cooled therein before entering the reservoir 19. The coil 38 serves as an inlet connecting the va'lve housing to the reservoir 19. A-t'i outlet from the reservoir 19 is alsoconnected to the valve housing. A third piston is interposed betweeen the pistons 33 arid 34 and connected thereto by a'r'od. There are spaces between the third piston and the other two, the one on the right? serving as passage means to connect the high pressure passageway to the inlet and the one on the left serving: to connect the outlet from the reservoir to the low pressure passageway. V

For the purposes of description of the operation of a complete system in accordancewith this invention, we can assume that the housing 14 of the pumps is rigidly secured, for example, to the body of a vehicle. The rotors of the pumps are positively connected to moving portions of the vehicle such, for example, as the wheels, If the valve 29 is moved to the opposite end of its path of travel from that shown in the drawing, and if the vehicle is moving, it will be. seen that the connection between thereservoir 19 and the pump inlets will be closed by the piston member 34 of valve 20 and that the outlet or. high pressure side of the pumps will be placed in free communication with the heat exchange coil 38. There will, therefore, be a path for the circulation of fluid extending from themanitold 33 to the valve 21, thence through high pressure line 25, valve 20, heat exchange coil 38, and reservoir 19. As long as the inlet is closed at the valve 20 by piston 34, there'will be no circulation of fluid in the system after the level in each of the pumps falls below a certain point. This is an important feature of the present inven-- tion as it results in practically zero loading on the pumps. Assume now, however, that it is desired to apply a braking force to the vehicle. If the valve 20 is moved partially back to the position shown in the drawing, the piston 33 will partially restrict the high pressure line and the piston 3 4 will partially open the inlet to line 26 from the reservoir 19. Under these conditions, a certain block the outlet in line 25, this circulating fluid is forced to pass through the heat exchange coil 38 before it returns to the reservoir 19. r It now the valve 20 is moved to the extreme end of its path of travel, as shown in the drawing, the rotors of all the pumps will be locked against further rotation. As long as the fluid pressure load on the rotors does not rise above a predetermined maximum, there will be no further circulation of fluid in the system. On the other hand, however, if the momentom of the vehicle is such that the predetermined pressure loading of the system is exceeded, the relief valve 22 will open and will remain in its open position until the system pressure falls below the predetermined value.

The applicability of the control system of this invention to clutches as well as brakes will be obvious to those skilled in the art. The basic concept of varying the fluid pressure load onthe rotor of a positive displacement pump lends itself admirably to such applications. Accordingly, while the present invention has been deseribed principally with reference to braking systems, it is not in fact limited thereto. The true scope is defined by the appended claims.

I claim:

1. A control system for subjecting the rotor of a positive displacement pump to variable fluid pressure loads between about zero and a value sufficient to lock the rotor, said system comprising in combination: a pump; a fluid reservoir including an inlet connection thereto andan outlet connection therefrom; a'high pressure passageway connected to said pump; a low pressure passageway connected to said pump; a pair of valve members;

housing means for said valve members connected to said inlet and outlet connections and to the ends of said passageways; means coupling said valve members togcther for movement in unison, said valve members having a sliding relation to said ends, the distance between means operable when one of said valve members is in open position to connect the high pressure passageway to the inlet connection, said one of said valve members being movable to render said passage means inoperative; and additional passage means operable when the other of said valve members is in open position to connect the low pressure passageway to the outlet connection, said other of said valve members being movable to render said additional passage means inoperative, and means in said housing means separating said passage means. I

2. A control system for subjecting the rotor of a reversible positive displacement pump to variable fluid pressure loads between about zero and a value sulficient to lock the rotor, said system comprising in combination:

a pump; a fluid reservoir including an inlet connection thereto and an outlet connection therefrom; a high pressure passageway connected to said pump; a low pressure passageway connected to said pump; a pair of valve members; housing means for said valvemembers connected to said inlet and outlet connections and to the ends of said passageways; means rigidly securing said members together as a unit, said unit being adjustable to'a position where one of said valve members will completely close the end of said high pressure passageway while the end of said low pressure passageway is fully open and to a position where the other valve member will completely close said low pressure passageway while the high pressure passageway is fully open; passage means operable when one of said valve members is in open position to connect the high pressure passageway to the inlet connection; said one of said valve members being movable to render said passage means inoperative; additional passage means operable when said other of said valve memhers is in open position to connect the low pressure passageway to the outlet connection, said other of said valve members being movable to render said additional passage means inoperative; automatic valve means connected to the other ends of said passageways and a pair of additional passageways each connected to. said pump at one end and to said automatic valve means at the other, said valve means being reversible and being operable in one position to connect said high pressure passageway to one of said additional passageways and said low pressure passageway to the other of said additional passageways and being operable on reversal to connect said low pressure passageway-to said one of said additional passageways andto connect said high pressure passageway to said other of said additional passageways and means operative on the reversal of said pump to reverse said automatic valve means. i

3. A system as definedinclaim 2 in which said pair of valve members are pistons mounted on a common rod, eachspaced laterally from .an opposite side of a third piston, mounted on said rod, said passage means being the spaces on opposite sides of the third piston.

, 4. A system as defined in claim 2, including a bypass connecting said inlet connection to said high pressure passage and bypassing said housing means, and escape valve means in said bypass, said escape valve meansineluding a valve element, a compression-spring urging.

said element to a closed position, adjustable means for 5 varying the compression on said spring and adjustable 2,042,539 means for limiting the length of movement of said valve 2,152,570 element and thus limiting the volume of flow through 2,551,677 said bypass. 2,681,713

References Cited in the file of this patent 5 UNITED STATES PATENTS 812 657 1,470,804 Buckingham Oct. 16, 1923 r 909,346

6 Maisch June 2, 1936 Scates Mar. 28, 1939 Hofr'strom May 8, 1951 Chambers June 22, 1954 FOREIGN PATENTS France Feb. 8, 1937 France Dec. 20, 1945 

